The present invention relates to duct work connectors and particularly to a device for joining sheets of insulating material so as to provide a fluid conducting duct.
The conventional insulated air transport ducts are formed from a sheet of insulating material which is four feet wide, ten feet long and approximately one and one-eighth inches thick. Typically a thin layer of reflective material such as aluminum foil is attached to one side of the sheet of insulating material. The sheet is then mitred, notched or grooved so as to produce a series of three cuts which run the entire length of the sheet and are spaced at one foot intervals across the width of the sheet. The depth of the cuts is adjusted so as to cut through substantially all of the insulating material while leaving the foil covering layer intact. Once the cuts have been made, the sheet may be folded into a square duct which is one square foot in cross sectional area and has the aluminum foil layer on the outside. The duct is then stapled and taped at the corners in order to retain the duct configuration and to preserve the insulating properties of the duct. Obviously wider sheets of insulating material can be used so as to make ducts of larger cross sectional area.
Fabrication of the duct in the foregoing conventional manner exhibits several shortcomings. First, assembly requires precise on-the-job measurements and the use of special tools and accessories.
Second, conventionally assembled duct work also requires reinforcement channels or plates in order to give the duct work sufficient support for suspension from overhead structural members. The foregoing factors increase the cost and installation time of the duct.
Third, the conventional duct has the aluminum foil layer on the outside with the fibrous insulating material forming the inner surface of the duct. The constant and/or rapid passage of air over this surface may cause the release of minute particules of insulation material into the air stream causing a potential health hazard.
Finally, even when the corner formations of the conventional duct work are securely stapled and carefully taped, the duct work is far from air tight. Heated air tends to cool in its passage through the duct and in air conditioning systems, cooled air tends to warm lessening thermal efficiencies.